Digital broadcasting has characteristics of providing multiple channels, high quality, and multiple functions. In particular, developments of multiplexing techniques have enabled concurrent combination of images, speech, and data irrespective of contents and sizes and transmission of them, and have formed a return channel through a modem to allow interactive services. Accordingly, digital data broadcasting has overcome the problems of conventional analog broadcasting and has provided multimedia services with high added value to viewers.
However, when security between a transmitter and a receiver is not guaranteed in digital data combined broadcasting, the commercial structure of the broadcasting cannot be maintained. Broadcasting service providers have attempted to bring out services that depend on advertisement for income by activation of multiple channels and professional channels, to provide quality broadcasting services to subscribers, and to provide charged broadcasting services such as Pay-TV or Pay-Per-View (PPV) to bill TV subscription fees, and they also desire to have their various multimedia data protected and have control of the subscribers who are authorized to have a right to view the data. To solve the problems, the CAS (Conditional Access System) has been developed.
The CAS is a system for allowing subscribers having a right to view TV programs to receive specific programs by introducing the concept of subscriptions to the broadcasting, and it deals with a process for each digital broadcasting receiver to determine which broadcasting program a viewer will receive. In the CAS, a transmitter transmits encoded program signals and an entitlement given to an individual receiving user or a specific group to a receiver, and the receiver controls the ability of the subscriber having entitlement to decrypt the signal by using a smart card attached to the receiver.
Also, the conventional terrestrial and satellite digital broadcasting set the conditional access to the contents or users to thereby provide a charged service. In this instance, a process for encoding a stream to which the conditional access is applied and a process for canceling the conditional access through an encoding key received by a charged subscriber through a mobile communication network or another encoding key assigned through a smart card can be performed.
In general terrestrial and satellite digital broadcasting, a transmitter for forming a main broadcast network is provided on the single frequency network (SFN), a shade area in which no service is received is generated within the main broadcast network, and a gap filler for servicing the shade area is provided to thereby solve the problem of the shade area in the main broadcast network. For example, in a satellite digital multimedia broadcasting (DMB) system, most regions are available for receiving signals from a satellite, and the gap filler is used to acquire a receiving region in the shade regions in which no direct signal receiving is allowed, such as regions in a subway, a tunnel, and a building.
In detail, when it is not easy to directly receive satellite signals on the ground side, that is, within the tunnel, underground, and building, the gap filler receives the satellite signals through a satellite signal receive antenna and starts broadcasting.
Main broadcasting stations represent broadcasting stations that function as a main center of the broadcasting network system, and they plan, produce, and transmit broadcasting programs. In Korea, radio broadcasting stations include KBS, MBC, CBS, BBS, PBS, SBS, and Keukdong Broadcasting, and television broadcasting stations include KBS, MBC, and SBS. The broadcasting stations located in Seoul are established to be their transmitters. Commercial broadcasting in the USA or Japan forms broadcasting networks through contracts, but Korean broadcasting systems have a single organization such as KBS or have the same capital system such as MBC and CBS, and hence the transmitters perform a strong role in the system and management in addition to broadcasting substantially as headquarters.
Further, a repeater station is an auxiliary station with less power consumption, and is also called a satellite station. Conventionally, a broadcasting station has a service region, that is, a designated broadcasting region, but since boundary regions have a weak radio wave arrival and blanket areas, the satellite station is installed for the boundary regions. It is installed at mountaintops for receiving radio waves from the transmitters, and it receives the waves through high-sensitivity receivers, electrically amplifies them, and broadcasts them as radio waves of different frequencies.
However, when a main broadcasting network service provider is different from a repeater service provider, the repeater service provider generates the cost of installing and maintaining a broadcasting network in the shade region, and the repeater service provider charges for the usage of the repeating network. That is, the repeater service must be a charged service for the purpose of activating the repeating network, but no appropriate treatment for the charged service has been provided up to now.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.